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Choroid plexus papilloma

Dr Abhilash Sandhyala and Dr Paresh K Desai et al.

A choroid plexus papilloma (CPP) is an uncommon, benign neuroepithelial intraventricular tumour which can occur in both the paediatric (commoner) and adult population. It is classified as a WHO grade I tumor if typical and WHO grade II if atypical. They are, fortunately, far more common than the more aggressive choroid plexus carcinoma (WHO grade III) which they out number 5 to 1 7. 

Epidemiology

The tumours account for approximately 1% of all brain tumours, 2 - 6% of all paediatric brain tumours and 0.5% of the adult brain tumours. Approximately 85% of all choroid plexus papillomas occur in children under the age of 5 years 4.

Clinical presentation

Significant hydrocephalus is very common - it is seen in over 80% of cases 4. Although the exact mechanism remains uncertain, it is believed to be due to a combination of  CSF over production and decreased arachnoid granulation resorption. 

An association with von Hippel Lindau disease is recognised (as well as the more frequently associated haemangioblastoma). 

Pathology

Choroid plexus papillomas are WHO grade II lesions and typically appear as cauliflower like masses 4. Microscopically they demonstrate papillary structures with a delicate fibrovascular core lined by columnar or cuboidal epithelial cells with vesicular nuclei. Their appearance is very similar to normal choroid plexus 7.

If 2 or more mitoses are present per 10 high power field, then the tumour is designated an atypical choroid plexus papilloma and is classified as a WHO grade II tumour 7. 

Markers
  • cytokeratin : may help distinguish from an ependymoma

Radiographic features

Unlike most other brain tumours, which are more common in the posterior fossa in children and supratentorial compartment in adults, the relationship is reversed for choroid plexus papillomas. In adults these tumours most often (70%) occur in the fourth ventricle. In the paediatric age group the lateral ventricles are the commonest location, with a predilection for the trigone. Third ventricular, cerebellopontine angle, parenchymal and even pineal region tumours have also been described.

CT

The tumours are usually well-defined lobulated masses, either iso- or somewhat hyperdense compared to the adjacent brain. There is associated hydrocephalus. They usually homogeneously enhance, demonstrating with an irregular frond-like pattern, resulting in a cauliflower-like appearance. If there is markedly heteregeneous contrast enhancement, a choroid plexus carcinoma should be suspected 4.

Fine, speckled calcification is seen within the tumour in approximately 25% of cases 4. 

MRI

The frond-like morphology of the tumour can usually be seen, especially following contrast administration. Varying degrees of associated hydrocephalus are also present in almost all cases.

  • T1 : typically isointense c.f. to adjacent brain. May be somewhat hypointense
  • T2 
    • iso to hyperintense
    • small flow-voids may be seen within the tumour
  • T1 C+ (Gd) : marked enhancement, tends to be homogenous
  • MR spectroscopy
    • decreased NAA
    • increased Cho
Angiography

Being very vascular tumours, these masses demonstrate intense vascular blush on angiography. Enlarged choroidal arteries may be seen feeding the tumour, with shunting 4.

Treatment and prognosis

Total excision should be the aim of therapy and is curative in a vast majority of cases. CSF seeding / spread is uncommon. 

Differential diagnosis

The differential is essentially that of choroid plexus tumours.

  • choroid plexus carcinoma (CPC) : can be very difficult on imaging alone
    • almost exclusively found in young children 7
    • heterogeneous contrast enhancement
    • may show parenchymal invasion
    • if parenchymal invasion is absent, then they are almost impossible to distinguish from CPP
  • choroid plexus metastases

When located in the posterior fossa in children (less common) other tumours to be considered include :

In adults consider :

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